The present invention relates to a bus switching structure and a computer using the bus switching structure. More particularly, the invention relates to techniques adapted advantageously to control connection of input/output (I/O) slots for use with Peripheral Component Interconnect (PCI) buses.
Computer systems, such as workstations and servers, increasingly are adopting a dual PCI bus arrangement to address high-speed processing requirements. An aim of implementing such a dual PCI bus arrangement is to distribute the loads evenly on the I/O buses thereof to enhance the performance of the entire computer system. This type of bus arrangement used on local buses in a computer system is discussed and illustrated in detail on pp. 70-71 in xe2x80x9cThe Latest PC Technologiesxe2x80x9d (Supplement to Nikkei Byte, a Japanese publication from Nikkei BP Co., Jun. 21, 1994). The publication describes features of the PCI bus.
Investigations and experiments of such bus arrangements led to the discovery of some problems specific to the dual PC bus arrangements intended for I/O bus load distribution. The major problems are as follows:
One problem occurs where each of a plurality of I/O devices is connected fixedly to one of two PCI buses. Thus, either of the PCI buses will tend to be more heavily burdened with loads depending on the frequency of use and duration of use of the particular PCI bus to which the I/O devices are connected then the other PCI bus. The un-balanced loads prevent the computer system from reaching its full potential.
Another problem occurs when, in accordance with actual use conditions, an operator attempts to rearrange the I/O slot connections to the PCI buses so that the two PCI buses will be used in a balanced manner. This, however, requires the operator to have specialized knowledge of computer hardware, particularly the disassembling of the enclosure of the computer system and the rearranging of cable connections. Further, rearranging I/O slot connections to balance the loads on the PCI busses takes time and effort. Worse, an error or mistake made during the rearrangement can disable the computer system or destroy its parts.
It is an object of the present invention to provide a bus switching apparatus and a computer for use with the bus switching apparatus which changes I/O slot connections to a desired I/O bus simply and in a short time depending on load fluctuations during actual use, such that loads are evenly distributed over I/O buses and the throughput of the computer is enhanced significantly.
In carrying out the invention and according to one aspect thereof, there is provided a bus switching structure including a switching unit and a switching controller. The switching unit is located interposingly between an I/O slot and a plurality of I/O buses. The switching unit either connects or disconnects the I/O slot to or from each of the I/O buses in accordance with a switching signal. The switching controller output the switching signal to cause the switching unit to connect the I/O slot to one of the I/O buses and to disconnect the I/O slot from any other I/O bus, thereby effecting connection switchover between the I/O slot and the I/O buses.
According to another aspect of the invention, there is provided a computer having a plurality of I/O buses, an I/O slot, and a bus switching apparatus for connecting the I/O slot to one of the I/O buses. The bus switching apparatus includes a switching unit located interposingly between the I/O slot and the I/O buses. The switching unit either connects or disconnects the I/O slot to or from each of the I/O buses in accordance with a switching signal. The bus switching apparatus also includes a switching controller which outputs the switching signal to cause the switching unit to connect the I/O slot to one of the I/O buses and to disconnect the I/O slot from the I/O bus, thereby effecting connection switchover between the I/O slot and the I/O buses.
With any of the inventive structures above, the switching controller need only perform switching operations of the switching unit to change the I/O slot connection to a desired I/O bus easily and in a short time.
According to a further aspect of the invention, there is provided a computer having a plurality of I/O buses, at least two I/O slots, and a bus switching apparatus for connecting the I/O slots to one of the I/O buses. The bus switching apparatus includes a plurality of switching units located interposingly between each of the I/O slots and the I/O buses. Each switching unit either connects or disconnects one of the I/O slots to or from one of the I/O buses in accordance with a switching signal. The bus switching apparatus also includes a switching controller which outputs the switching signal to cause the switching units to connect each of the I/O slots to one of the I/O buses and to disconnect the I/O slots from the I/O bus, thereby effecting connection switchover between the I/O slots and the I/O buses.
With the inventive structure above, the switching controller need only carry out switching operations of the switching units to increase or decrease flexibly the number of I/O slots connected to a desired I/O bus.
Any one of the above-described structures of the invention permits switching the I/O slot connection to a desired I/O bus easily, quickly and flexibly. This helps to increase the throughput of the computer. The inventive structures eliminate the need for disassembling the computer enclosure or rearranging cable connections at the time of changing I/O slot connections. Further there can be no mistakes or errors when performing rearrangement that would disable the computer or destroy its parts inadvertently is eliminated. Thus, by use of the invention, anyone without specialized knowledge of computer hardware can perform the switching of I/O slot connections.